Open Source Touch Screens To The Rescue

Casey Hare | EDN Network | April 7, 2014

"We should have called you earlier. We need a stand-alone electronics box that can connect to our data logging systems, drive the main mechanism motor and measure a few other sensors. We're very worried about the end customer damaging the hardware so we're going to need voltage limits, torque limits and other safety features that change over the mechanism travel…and we need it right away. Also, we haven't specified the motor or sensors yet."

This was one of my favorite clients talking so I want to give them everything they wanted, but already the project sounded like a mess. We didn't know anything, we needed safety features we couldn't even imagine yet, and they'd just started building the mechanism and we need it right away. On top of everything, they needed the devices to run stand-alone, so it needed a user interface.

With some digging I was able to identify most of the hardware interfaces without much trouble. Now I had are range of reasonable voltage levels, current levels, sensors types and the rest. However, the safeties were still a long way off. Voltage and current limits equate to feedback loops running somewhere, but without the hardware to measure them there was no place to start. The mechanism was complex enough that my rough analytical models weren't going to be good enough. I needed electronics that were flexible enough to run the system once it was built, measure the signals through the mechanism actuation, and implement the necessary safety features. That sounds like firmware to me and because the system is relatively low bandwidth and in a serious hurry: Hello Arduino.